Round heart disease (RHD), a presumed viral myocarditis of turkeys, has been found to resemble, hemodynamically, congestive cardiomyopathy of humans. The radioactive microsphere technique will be used to systematically study regional myocardial blood flow in anesthetized turkeys with acute and chronic RHD, turkeys which have recovered from the disease, and control turkeys. Non-invasive echocardiographic techniques will be used to evaluate left ventricular function in these same groups, both awake and anesthetized. We intend to determine whether regional blood flow abnormalities are present in any or all stages of RHD and thereby to define the role of regional myocardial blood flow abnormalities in the pathogenesis of this disease. The samples used for blood flow measurement will also be examined histologically to assess the degree of cellular infiltration and/or fibrosis. The effect of drugs known to alter regional myocardial blood flow, or to have an anti-inflammatory action (hypertonic mannitol, nitroglycerin, nitroprusside, and corticosteroid hormones) will be evaluated at appropriate stages of the disease using sequential echocardiographic examinations and microsphere injections.